Enables ATPase binding activity. Predicted to be involved in cellular protein metabolic process; granzyme-mediated apoptotic signaling pathway; and response to UV. Predicted to act upstream of or within several processes, including proteasome-mediated ubiquitin-dependent protein catabolic process; protein ubiquitination; and ventricular trabecula myocardium morphogenesis. Predicted to be part of ubiquitin ligase complex. Predicted to be active in cytoplasm and nucleus. Orthologous to human UBE4B (ubiquitination factor E4B). [provided by Alliance of Genome Resources, Apr 2022]